A new exploitation technique called key reinstallation attacks (KRACK) affecting WPA2 has been discovered. A remote attacker within Wi-Fi range could exploit this attack to decrypt Wi-Fi traffic or possibly inject forged Wi-Fi packets by reinstalling a previously used group key (GTK) during a group key handshake.

A new exploitation technique called key reinstallation attacks used to break Wi-Fi handshakes that negotiate session keys was discovered. These attacks target the Wi-Fi/WPA2 standard. An adversary can trick a client or Access Point (AP) into reinstalling an already-in use group key in the group key handshake. While reinstalling the already in-use key, the associated packet number (sometimes also called nonce) and receive replay counter is reset. This causes nonce reuse, voiding any security the underlying encryption protocol is supposed to provide. For example, it allows decryption or injection of frames, and enables an attacker to replay frames.